1. Field of the Invention
The present invention relates to indicator gauges, and more particularly to blood pressure indicator gauges employed in conjunction with blood pressure measuring equipment, where a blood pressure measuring sleeve is applied to a limb and the pressure values and other variables are transmitted to a monitoring console. The special pressure indicator gauge of the invention is adapted for the measurement and recording of two different pressure values by means of two independent pointers which can be blocked at given reading values in response to appropriate signals.
2. Description of the Prior Art
Blood pressure gauges of the above-mentioned type are known in the prior art. They generally feature a rotatable pointer on a pointer shaft to which is attached a return string opposing the movement of the pointer in response to an increase in pressure in a pressure capsule whose expansion drives the pointer shaft via a suitable lever and gear transmission. Such a gauge may further include pointer blocking means consisting of a solenoid and of a blocking member connected to the gear transmission and reaching into the field of the solenoid, for the latter to stop and hold the rotating assembly.
For blood pressure measuring purposes, this type of gauge is normally specially adapted to have two pointers, in order to indicate and record the systolic and diastolic blood pressures of a patient. As the blood pressure measuring sleeve is pressurized, the same pressure also expands the measuring capsule, and this expansion is transmitted to the pointers by means of a suitable translating drive. The latter normally includes a lever converter whose movements are transmitted by a drive arm to a gear segment of large radius which, by engaging a small gear on the pointer shaft, moves the latter in accordance with the pressure acting inside the measuring capsule. The pressure translating drive may further include a drive pin extending laterally from the gear segment and reaching into engagement with a similar second gear segment, engaging a second small gear on the shaft of a second pointer. The shaft of this second pointer is a hollow shaft arranged concentrically with the shaft of the first pointer and located axially between the pointer and gear of the first shaft. In most cases, the hollow shaft is journalled on the shaft of the first pointer. Each pointer is further associated with blocking means consisting of a segment-shaped flat blocking member attached to the large-radius gear segment, and of a blocking solenoid arranged near the periphery of the blocking member, the blocking solenoid being electrically controllable by means of suitable switches. If, following the pressurization of the blood pressure measuring sleeve to a sufficiently high starting value, the pressure in the sleeve and in the measuring capsule is reduced at a controlled rate, both pointers will return under the action of their return springs in accordance with the motions of the translating mechanism, until the blocking solenoid for the second pointer is energized in response to a control signal from the blood pressure measuring device, thereby blocking the second pointer, while the first pointer, continuing its movement, is later similarly blocked by means of its associated blocking solenoid. The blocked positions of the two pointers indicate the systolic pressure and the diastolic pressure, respectively.
Known prior art blood pressure indicator gauges of the aforementioned type have the shortcoming, however, that a certain inaccurancy of reading results from the fact that, although the pointer blocking devices respond quickly, the pointers themselves, which move in response to the geared translating drive in one or the other direction, lag in position behind the actual pressure values by a noticeable amount. This means that the pressure value indicated by a pointer may differ as much as 10 mm Hg from the actual pressure value. Such a deviation from actual pressure values is in many cases unacceptably high.